Fresh fruits and vegetables typically have a very short harvest season and spoil quickly. Canning is one method of preserving perishable fruits and vegetables. During post-harvest production, canned fruits and vegetables are packed in water, or a liquid syrup, or juice or brine, hermetically sealed, and thermally processed to achieve commercial sterility. Production of canned fruits and vegetables typically takes place within days or weeks of harvest. There is a strong commercial interest to be able to pack canned items throughout the year, not just during harvest. One method of year-round production is to use frozen fruits and vegetables in place of fresh produce in canning operations. However, when compared to fresh produce, frozen fruits and vegetables that are later thermally processed have relatively poor texture. Canning frozen fruits and vegetables worsens the texture because the thermal process softens the produce further. For these reasons, there is also a strong commercial interest in developing a method that would allow production of canned items with consumer accepted texture from individually quick frozen (“IQF”) fruits and vegetables.
Some fruit and vegetable manufacturers add calcium salts to certain products to improve texture. The FDA specifies which calcium salts are allowed in food products. For example, the Standard of Identity for canned berries allows for inclusion of calcium salts. Federal Regulations (21 C.F.R. §145.120) allow calcium salts as firming agents provided that the calcium salt added is no more than 0.035 percent of the weight of the finished canned berries. Among the products that are allowed by the FDA to contain calcium salts for firming, adding calcium is considered common practice, but it is not universal in the industry.
Calcium salts may be added to products using one of the following methods: spraying or dipping fruits or vegetables as pretreatment and adding calcium in the topping of finished products. Existing manufacturing techniques to enhance texture and firmness of fruits and vegetables produce soft fruits and vegetables. For example, U.S. Pat. No. 5,939,117 teaches application of a preservative of calcium ions, ascorbate ions—or both—as a solution or in dry form to fresh fruit, such as apple slices, and then storing the fruit covered with the preservative in a container between −7° C. and 30° C. The preservative can be applied by spraying, dipping, sprinkling, tossing, immersing, or drenching. Immersing or dipping the fruit must be limited to no more than 5 minutes because the preservatives can adversely impact fruit flavor.
In another example, U.S. Pat. No. 4,336,273 teaches preserving fruit or vegetables by exposing them to a spray, vapor, or pool of organic compounds, such as, aldehydes, amides, esters, hydrocarbons, halogenated hydrocarbons, ketones, etc., for 10-20 minutes between 0° C. to 75° C. Preservation with this technique requires washing or rinsing the organic compound from the fruit or vegetable prior to heat processing. The flavor of the fruit or vegetable may be adversely affected by overexposure to the organic compound if not washed or rinsed properly.
In yet another example, U.S. Pat. Nos. 5,645,879 and 5,843,511 teach blanching fruits and vegetables before conventional sterilization. Blanching may occur in a solution with food-grade multivalent salt compounds or food-grade acids—or both—and must be carefully regulated to avoid adversely affecting firmness of the fruit or vegetable. Blanched fruits or vegetables must also then be properly cooled by immersion in cold water to stop enzyme activity on the flesh of the fruit or vegetable.
In a further example, European Patent Application No. 0853886 teaches wetting fresh or frozen fruit with an aqueous system containing at least as much sugar and as many calcium ions as the liquid phase of the fruit for no less than 2 days at temperatures above the freezing point of the aqueous system and less than 10° C.
The aforementioned processes have the following disadvantages: soft post-preservation texture and complex manufacturing steps, such as, sensitive blanching temperatures, precise rinsing schedules for food-grade salts or acids to avoid flavor degradation, or use of organic compounds that must be carefully rinsed at precise times.
Consumers are becoming more health conscious. Demand for fruits and vegetables in daily consumption have increased. There is a strong commercial interest to have year-round industrial processing capacity for preserving high-quality fresh fruits and vegetables.
There is currently no method available that allows manufacturers to thermally process IQF fruits or vegetables that yield an acceptable texture post-sterilization. The invention enables this. It provides firmly-textured, high quality fruit and vegetable products after thermally processing IQF products.